MECHANICS. 



[Lesson L 



o this woman." He made several orreries; and, in 1747, commenced publishing his 

 works. The following year, lie began to deliver lectures on astronomy, and, subse- 

 quently, on mechanics, hydrostatics, hydraulics, pneumatics, and electricity. He died 

 in 1766, in the sixty-sixth year of his age, worth about 6,000 in property and cash, 

 having received 50 a year from the Privy purse for many years. He was very 

 properly elected a Fellow of the Royal Society for his scientific acquirements. ~\Ve 

 must acknowledge, that, however much astronomy, and the other branches of science, 

 were indebted to his untiring perseverance and research, yet he rendered most essential 

 service to the study of MECHANICS. 



MECHANICS. 



QUESTIONS AND EXPLANATIONS. 



1. T. WHAT do you mean by Me- 

 chanics ? 



P. It is the Philosophy of Machinery, 

 or the Theory of Powers or Forces, being 

 a science which teaches us the proportion 

 of the forces, motions, velocities, and even 

 the actions of bodies upon one another, 

 either directly or by means of machinery. 



2. T. What is the term mechanics de- 

 rived from ? 



P. From the Greek meelcanee (M7jx"^)> 

 vhich signifies a machine. 



3. T. What do you mean by force ? 



P. The power exerted on a body to 

 make it change its position. 



[The pupil should read Q. 131, 132, and 133, 

 p. JM.] 



4. T. What do you mean by a ma- 

 chine ? 



P. In the sense it is here employed, I 

 mean any mechanical instrument by which 

 force may be made to act. 



5. T. How is this accomplished ? 



P. Machines can only convey the mo- 

 tion imparted to them to another body; 

 they cannot act of themselves, but may 

 regulate or modify the force employed, 

 although they cannot produce it. 



[Pupils should study Lesson X., p. 24, and then 

 they will be better prepared to understand 

 what is meant by motion, force, velocity, &c.] 



6. T. Explain what you mean by the 

 term mechanical. 



P. Mechanical action is the result of 

 the application of power or force acting 

 upon a body. For example [Experiment 

 1], if 1 rub a metal button upon a brick 



for some time, the metal is reduced in 

 thickness by the mechanical action of the 

 particles of brick ; again, [Experiment 2] 

 if a tin can, with a small hole in the bottom 

 of it, is filled with water, and placed about 

 two feet above the brick we have just used, 

 and allowed to remain there for some time, 

 the water will act mechanically upon the 

 brick, and wear it away. 



7. T. Have not some philosophers di- 

 vided the science of mechanics, or as Dr. 

 Wallis terms it, the " Geometry of motion," 

 into two parts ? 



P. Yes, into STATICS and DYNAMICS ; 

 but it is better to consider the subject as a 

 whole, and not adopt this mode of dividing 

 it. 



8. T. What is meant by Statics, and 

 what is the term derived from ? 



P. Statics is the doctrine of the equi- 

 librium of forces, and the term is derived 

 from the Greek verb stao (Sracw), to stand. 



9. T. What is the word Dynamics de- 

 rived from, and what is its signification ? 



P. It is derived from the Greek word 

 (liin(t)iiis (AIJVU/J.IS), force or power, and lite- 

 rally means the theory of force and power. 



10. T. When we have to apply a ma- 

 chine, what are the chief things to be 

 considered ? 



P. 1. The force which we have to over- 

 come, sustain, or oppose. 2. The force 

 which will enable us to overcome, sustain, 

 or oppose the resisting force. 3. The ma- 

 chine by which the desired eflect is pro- 

 duced, by transmitting the requisite force 

 or power to the resisting force. 



